VRF Verification Library for WASM contracts

A minimal, optimized VRF proof verification library specifically designed for smart contracts on WASM-based platforms like NEAR, and others.

Features

• Minimal Dependencies: Only essential crypto libraries, no RNG or signing
• No-std Compatible: Works in constrained smart contract environments
• Multi-Platform: NEAR, and generic WASM support
• Size Optimized: ~10KB compiled size vs 100KB+ for full libraries
• Conditional Compilation: Only include platform-specific code when needed
• Battle Tested: Uses proven verification logic from FastCrypto

Installation

Generic WASM Contracts (Default)

[dependencies]
vrf-contract-verifier = "0.8"

NEAR Smart Contracts

For NEAR smart contracts with enhanced features:

[dependencies]
vrf-contract-verifier = { version = "0.8", features = ["near"] }

Using with VRF-WASM for Proof Generation

To use both libraries together, you must enable the browser feature in vrf-wasm for your tests and the near feature for contract builds.

For cargo test:

# In your dev-dependencies
vrf-wasm = { version = "0.7", features = ["browser"] }

For NEAR contract builds:

# In your dependencies
vrf-wasm = { version = "0.7", default-features = false, features = ["near"] }
vrf-contract-verifier = { version = "0.7", features = ["near"] }

This setup ensures your tests use the browser-compatible RNG while your contract uses the NEAR-specific RNG.

Quick Start

Basic Usage (Generic WASM)

use vrf_contract_verifier::{verify_vrf, VerificationError};

// Verify a VRF proof (80 bytes: gamma(32) + challenge(16) + scalar(32))
let result = verify_vrf(proof_bytes, public_key_bytes, input_bytes);
match result {
    Ok(vrf_output) => {
        // VRF proof is valid, use the 64-byte output
        println!("VRF output: {:?}", vrf_output);
    }
    Err(VerificationError::InvalidProof) => {
        // Invalid proof
    }
    Err(e) => {
        // Other verification errors
    }
}

NEAR Smart Contract

use vrf_contract_verifier::{verify_vrf_bool, verify_vrf};

#[near_bindgen]
impl MyContract {
    // Simple boolean verification
    pub fn verify_randomness(&self, proof: Vec<u8>, pk: Vec<u8>, seed: Vec<u8>) -> bool {
        verify_vrf_bool(proof, pk, seed)
    }

    // Full verification with VRF output
    pub fn verify_and_get_output(&self, proof: Vec<u8>, pk: Vec<u8>, seed: Vec<u8>) -> Option<Vec<u8>> {
        match verify_vrf(proof, pk, seed) {
            Ok(output) => Some(output.to_vec()),
            Err(_) => None,
        }
    }
}

API Reference

Core Verification Functions

verify_vrf(proof_bytes, public_key_bytes, input) -> Result<VrfOutput, VerificationError>

Complete VRF verification returning the 64-byte VRF output on success.

verify_vrf_fixed(proof_array, public_key_array, input) -> Result<VrfOutput, VerificationError>

Type-safe version using fixed-size arrays instead of Vec.

verify_vrf_bool(proof_bytes, public_key_bytes, input) -> bool

Simple boolean verification for contract usage.

Build Examples

# Build without any platform features (smallest)
cargo build --target wasm32-unknown-unknown --release

# Build for NEAR contracts specifically
cargo build --target wasm32-unknown-unknown --features near --release

# Test all configurations
cargo test                                   # Basic features
cargo test --features near                   # With NEAR features

Important Notes

• Feature Compatibility: When using both vrf-wasm and vrf-contract-verifier in the same project, ensure consistent feature flags
• NEAR Runtime: The near feature enables NEAR-specific optimizations but requires NEAR runtime for execution
• Cross-Verification: Both libraries use identical cryptographic implementations for compatibility

Platform-Specific Build Optimization

The crate uses conditional compilation to minimize dependencies:

// NEAR-specific serialization only when needed
#[cfg_attr(feature = "near", near_sdk::near(serializers = [borsh, json]))]
pub struct VrfProof { ... }

// Platform-specific dependencies only when features are enabled
#[cfg(feature = "near")]
use near_sdk;

Compatibility

VRF Suite

Compatible with Sui VRF implementation:

• Suite string: sui_vrf
• Curve: Ristretto255
• Hash: SHA-512
• Challenge length: 16 bytes
• Output length: 64 bytes

Smart Contract Platforms

• ✅ NEAR Protocol
• ✅ Generic WASM contracts

Security Notes

• This library only performs verification - does not generate keys or proofs in contracts
• Verify proofs were generated with proper randomness
• Consider replay attack protection in contract logic

License

Apache-2.0